The approval is based on the results of a single, open label, randomized, multinational study that enrolled 463 patients with metastatic colorectal cancer. Patients were randomly assigned to either best supportive care (BSC) alone or BSC plus panitumumab, 6 mg/kg intravenously, every other week. All patients were required to have disese progression following one or more chemotherapy regimens containing a fluoropyrimidine, irinotecan, and oxaliplatin. Confirmation of eligibility (disease progression following an adequate course of treatment) was verified for 75% of the patients based on a review of source documents by an external committee masked to treatment assignment.

The progression and response evaluations were based upon review of radiographs and other source documents by the same independent review group. The mean progression-free survival was 96 days for patients receiving panitumumab and 60 days for patients receiving BSC alone however, the median times to progression were similar (approximately 8 weeks.). There were 19 partial responses (8%) among the 231 patients randomly assigned to panitumumab; the median response duration was 17 weeks. There was no difference in overall survival between the two study arms. Approximately 75% of patients in the BSC alone arm crossed over to receive panitumumab after a determination of disease progression by the study investigator. The majority of patients' tumors exhibited EGFR expression in ≥10% of tumor cells with no evidence of a correlation between either the proportion of cells expressing EGFR or the intensity of EGFR expression. The most serious toxicities identified in clinical studies of panitumumab were pulmonary fibrosis, severe dermatologic toxicity complicated by infectious sequelae and septic death, infusion reactions, abdominal pain, hypomagnesemia, nausea, vomiting, and constipation. The most common adverse events were skin rash, hypomagnesemia, paronychia, fatigue, abdominal pain, nausea, and diarrhea.

This summary was provided by Richard Pazdur, M.D., director of the FDA's Division of Oncology Drug Products.

The FDA is the division of the U.S. Department of Health and Human Services charged with ensuring the safety and effectiveness of new drugs and other products. (See "Learn How Drugs and Devices Get Approved.") The FDA's mission is to promote and protect the public health by helping safe and effective products to reach the market in a timely way, and monitoring products for continued safety after they are in use.